docs: refresh CLAUDE.md Tesseract and testing sections

[melonamin]

CLAUDE.md drifted from the codebase in three places, which recently sent issue #89 triage in the wrong direction:

• The Tesseract section described a stub implementation and Scripts/build-tesseract.sh / download-tessdata.sh / app-store-prepare.sh, none of which exist anymore. The integration ships via the TesseractSwift package with on-demand traineddata downloads; the section now documents that.
• The Testing section claimed the project has no test suite. TRexCore has an XCTest suite; the section now points to it and how to run it.
• The CLI build command referenced scheme "TRex CMD"; the scheme is named "TRex CLI" (the directory is still TRex CMD/).